Bug: (Exception occurs in markdown/no-missing-label-refs when links from the second onwards have undefined labels)

[Ymmy833y]

Environment

ESLint version: 9.12.0
@eslint/markdown version: 9.12.0
Node version: 20.9.0
npm version: 10.8.3
Operating System: Windows 11

Which language are you using?

commonmark

What did you do?

Configuration

import markdown from "@eslint/markdown";

export default [
    {
        files: ["**/*.md"],
        plugins: {
            markdown
        },
        language: "markdown/commonmark",
        rules: {
            "markdown/no-missing-label-refs": "error",
        },
    }
];

1. Create a Markdown file with the following content:

   [Foo][foo]
   [Bar][]

2. Enable the @eslint/markdown plugin and the markdown/no-missing-label-refs rule in your ESLint configuration.
3. Run ESLint on the Markdown file.

What did you expect to happen?

  1:7  error  Label reference 'foo' not found  markdown/no-missing-label-refs
  2:2  error  Label reference 'Bar' not found  markdown/no-missing-label-refs

What actually happened?

ESLint throws the following exception and stops execution:

Oops! Something went wrong! :(

ESLint: 9.12.0

TypeError: Cannot read properties of undefined (reading 'length')
Occurred while linting ...\eslint-markdown-sample\docs\sample.md:1
Rule: "markdown/no-missing-label-refs"
    at findMissingReferences (.../eslint-markdown-sample/node_modules/@eslint/markdown/dist/esm/index.js:1509:25)
    at text (.../eslint-markdown-sample/node_modules/@eslint/markdown/dist/esm/index.js:1580:9)
    at ruleErrorHandler (...\eslint-markdown-sample\node_modules\eslint\lib\linter\linter.js:1084:48)
    at ...\eslint-markdown-sample\node_modules\eslint\lib\linter\safe-emitter.js:45:58
    at Array.forEach (<anonymous>)
    at Object.emit (...\eslint-markdown-sample\node_modules\eslint\lib\linter\safe-emitter.js:45:38)
    at NodeEventGenerator.applySelector (...\eslint-markdown-sample\node_modules\eslint\lib\linter\node-event-generator.js:297:26)     
    at NodeEventGenerator.applySelectors (...\eslint-markdown-sample\node_modules\eslint\lib\linter\node-event-generator.js:326:22)    
    at NodeEventGenerator.enterNode (...\eslint-markdown-sample\node_modules\eslint\lib\linter\node-event-generator.js:337:14)
    at runRules (...\eslint-markdown-sample\node_modules\eslint\lib\linter\linter.js:1128:40)

Link to Minimal Reproducible Example

https://stackblitz.com/edit/stackblitz-starters-bhmkmm?file=package.json

Participation

• I am willing to submit a pull request for this issue.

Additional comments

Failing Test Case

The following test case results in the exception being thrown:

// tests/rules/no-missing-label-refs.test.js

invalid: [
    {
        code: "[Foo][foo]\n[Bar][]",
        errors: [
            {
                messageId: "notFound",
                data: { label: "foo" },
                line: 1,
                column: 6,
                endLine: 1,
                endColumn: 9,
            },
            {
                messageId: "notFound",
                data: { label: "Bar" },
                line: 2,
                column: 2,
                endLine: 2,
                endColumn: 5,
            },
        ],
    },
],

Other Cases Where the Error Occurs

1. Case 1

   [Foo][]
   [Bar][]

2. Case 2

   [Foo][foo]
   [Bar][bar]
   [Hoge][]

3. Case 3

   [Foo][foo]
   [Bar][]
   [Hoge][hoge]

Cases Where No Error Occurs

1. Case 1

   [Foo][]
   [Bar][bar]

2. Case 2

   [Foo][foo]
   [Bar][bar]

3. Case 3

   [Foo][]
   [Bar][bar]
   [Hoge][hoge]